Sage Gedde Ignition - Buzz coil add-on?

[Admiral_dk]

I specifically referred to Don's first shown schematic and on that the 555 is running as an astable multivibrator (oscillator)- having a 1mS. firing time and an adjustable delay before next auto firing ~ this kind off a trembler, running all the time.
The circuit the the right of the 555 is an current amplifier where the right most transistor is a high voltage device (and they usually requires quite a bit of current as input).

My first suggestion cuts the signal to the current amplifier when a spark isn't required and my second suggestion shorts the firing signal for the duration of not wanting fire.
None of them gives a perfect firing timing as they haven't got any influence on where the oscillator is in it's sequence, but if the firing is as rapidly as the coil can sustain it will not matter on a slow running engine - but would be a problem over a certain RPM ....

I hope that I have explained it in an understandable way (I'm an Electronic Technician by education and profession). If not, please ask and I'll try to do better 

Excuse me Don, I didn't catch that first time as I was still thinking about having it work as a kind of tremble circuit. You kind of converted it into a traditional Ignition system (kind of my first attempt many years ago) 

[Don1966]

We all have our days Per.....


Don

[Admiral_dk]

Ups - got caught out on what can happen to a posting when editing what I just posted and somebody else post in the meantime .... newer had that happen before .... and sorry for the not so logical answer.

[Admiral_dk]

Oh yes we do Don 

[MJM460]

Hi Don, thank you for explaining that, it makes sense now.

I think I will stick to thermodynamics, but I have enjoyed dabbling in electronics in a very low key way since I was teenager.   I like to try and understand how these things work.  Comes in handy for ignition circuits and governors and the like.

MJM460

[pmerritt]

Thanks for the interesting discussion everyone! Sadly, I still don't really understand everything. I would probably be helpful if I provided the circuit I'm trying to control. There is an old and long discussion on HMEM about it and it was subsequently published in Model Engine Builder #34. I'm not sure what is appropriate to share here. It probably doesn't help that I don't fully understand how the basic circuit works. There is a transistor that feeds the gate of an IGBT that tells the coil when to charge/fire. What exactly is happening to current and voltages I don't know. The transistors tell the coil to fire in response to the hall trigger going LOW (I think. I guess it could be on the return to HIGH but I don't think that is what I'm actually seeing when testing). I'm stuck on how to turn the oscillator ON when the triggered Hall sensor output is LOW. In the control circuits I've seen online and the experiments I've done, this is the opposite of what the oscillator needs to be turned on. I know there must be a way to get this to work but my ability to implement that is hampered by my rudimentary (at best) knowledge of electronics. I will be at my company's home office this week and should have a chance to discuss this in person with someone who knows a lot more about electronics than I do. If I ever find a way to make this work, I'll let everyone know.

Peter

[Admiral_dk]

I'll gladly help you, but I need to see the schematic to do so ....

So if you got one that you can't 'Publish' - try to send me a PM with it attached and I'll see what I can come up with.

Best wishes

Per